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Патент USA US2120995

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June 21, 1938.
A. VAN- DE RlET
2,120,995
AMPLIFYING ARRANGEMENT
Filed Jan. 25,_ 1933
.1
INVENTOR
'
ABFaAHAM VAN DE RIET
ATTORNEY
2,120,995
Patented June 21, 1938
VUNITE’D ‘STATES PATENT oFFics
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7'
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2,120,995
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Abraham van de Biet, Eindhoven, Netherlands,
,assignor to Radio Corporation of America a
corporation of Delaware
.
"Application
.
I In the
January
Netherlands
23, 1983,-‘Serial
April 26, 1932
No.~a652,996‘
'
.
5 Claims.
(Cl. 179L171“).- .
feeble signals, also, the direct current energy
the alternating current energy delivered by an
delivered is smaller than in the case of power
amplifying valve without the mean anode dis
sipationv being exceeded.
At a given anode dissipation the alternating
current energy delivered by an amplifying valve
can only be increased if at the same time the
7 direct current energy delivered'is reduced. A re-'
ii) duction of the direct current energy in the output
circuit can be obtained at a given anode voltage
by the use of a negative grid bias. The value of
this grid bias is, however, limited by the condi
tion that the valve should always operate on a
15
This arrangement ensures that in the case of
This invention has reference to amplifying ar
rangements, and provides means for increasing
linear part of the‘ anode current-grid voltage
ful signals. Thus, the total direct current energy
delivered decreases when receiving weak signals, UK
whereas, the alternating current energy delivered
remains unvaried so that the total quantity of
energy delivered is reduced, and the tube is not
fully loaded. . Consequently, the primarily im
pressed signal voltage can be increased. This
results in an increase of anode direct and alter
nating current energy until the admissible load
of the tube is reached again.
The circuit arrangement according to the in
vention is particularly’ advantageous for valves 15
characteristic curve. That is to say, the algebraic having to deliver a high power; consequently, for
sum of the negative grid bias and the maximum ‘ example, for the last valve,v in an amplifying cir
alternating voltage to be ampli?ed should not be cuit arrangement. The alternating current
so large that the valve operates on a curved part energy deliverediby a given type of amplifying
valve is increased by the use of the invention.
20
of the characteristic.
‘
‘In order that the invention may be clearly
In well known circuit arrangements, generally,
constantvoltages are supplied to the anode and understood and readily carried into effect two
grid of the amplifying valve. The value of these embodiments thereof will now be described more
voltages is dependent upon the conditions that fully with reference to the accompanying draw
ing, in which:
'
25
a given anode dissipation should not be ex
,Fig. 1 shows thelast amplifying stage of a bat
ceeded, and that a certain maximum voltage
shouldbe ‘susceptible to. a. linear ampli?cation. tery receiver embodying the invention;
‘Independently of the value of the alternating
Fig. 2 shows a modi?cation employing power
voltage vto be ampli?ed at a given moment, a, amplifier supplied with alternating current.
constantdirect current energy'is delivered by a
Referring to Fig. 1, I designates ‘a thermionic‘
valve adjusted in the manner .of said well'known valve illustrated as a screen grid valve. vIts input
circuit includes an impedance 2 which is, forex
ample, the secondary of a transformer to which
which the direct current energy delivered is not , thevoltages to be ampli?ed are supplied. The
constant, and in which this energy is, smaller output circuit of the valve includes anoutput im
than in the. case above described so that a higher pedance 9; for example, the primary of a transa
alternating current energy can be admitted for a former to which a loudspeaker may be connected.
given valve. The amplifying arrangement, ac
The screen grid is connected to a point of the,
cording to the invention,’ is characterized by a anode voltage battery (not shown to preserve
40
grid bias which is so variable with the signal
_
_ ,
voltage to be ampli?ed that when the signal simplicity of disclosure).
arrangements.
,
l
..
.
.
The invention provides for an arrangement in
40
voltage decreases the grid bias becomes more
negative.
‘
Thus, in thecase of ‘feeble signals; a high, and,
in the, case of more powerful signals, a lower
negative grid bias is applied to the ampli?er valve.
In any case this grid biasv should besuch that the
algebraic sum of the bias and of the voltage to be
ampli?ed is smaller than a voltage by which the
, valve would be adjusted to a curved partof the
characteristic curve.’ Preferably, the adjustment
is such that the. sum hereinbefore indicatedof.
the grid voltages is substantially constant, and is
so large as to prevent :thevalve 'fromiop'erating
55 , onacurved part of the characteristic,
The valves used may comprise directly, or in
directly,‘ heated cathodes which are supplied with
direct, or alternating, current. Generally, it is
desirable to withdraw the voltages to be recti?ed 45
fromthe output circuit of the ampli?er, as the .
voltages which occur in the input [circuit are
often too small to ensure a proper control, and
moreover, a connection of the recti?er in parallel
with the input. circuit results in a rather great 50
decrease of the ampli?cation. Generally, there
fore, a part of the output voltage will be recti
?ed, and in this .caseisaid part should be so large
that-the grid voltage of the amplifying valveiis
constantly as much as ‘possible negative but 55
2,120,995
always so that no operation ensues in a curved
the negative bias of grid I is reduced by the
part.
positive voltage across resistor 4|. Each of re
sistors 4|] and 4| is shunted by a condenser of
.
The diagram shown in Fig. 1 represents the
last stage of a battery ampli?er and can be used,
for example, in a portable set. Such a device is
always supplied with direct current. In this case
it is important that the cathodes of all the valves
should be connected to the same source of voltage.
This condition is satis?ed in the circuit arrange
10 ment illustrated.
A triode I2 which is connected
low impedance to signal currents.
Resistor Ell
functions as a high impedance to signal cur
rents; condenser 5| is a path of low impedance
to current from source 3I.
While I have indicated anddescribed several
systems for carrying my invention into effect, it
will be apparent to one skilled in the art that
as a grid detector is used as the recti?er. The
my invention is by no means limited to the
anode circuit of this valve includes a high resist
particular organizations shown and described,
ance I3. When no signal is impressed on the in
but that many modi?cations may be made with
put circuit 2 of valve I, the anode current of valve 7 out departing from. the scope of my invention as
I2 is a maximum.
‘set forth in the appended claims.
15
The potential drop across the resistance I3 is ‘ " What is claimed is:
thus high, and the voltage at the plate of valve
I2 is consequently low. This voltage .summed up
with the voltage of battery I‘! is supplied to the ,
20 grid of valve I by means of a potentiometer M,
I5, H3; Thus, the negative grid voltage of this
valve is rendered a maximum, but the grid voltage
is not negative enough to operate the tube on the
curved portion of the characteristic. Now, if an
25 alternating voltage is supplied to the input cir
cuit of valve I, this results in that the voltage at
the input circuit of the detector is lowered, the
current passing through resistance I3 decreases,
and the voltage at the plate of valve I2 conse
30 quently increases. Thus, the grid voltage of valve
I becomes less negative. The grid bias is
smoothed by means of condensers I8 and Ill.
The condensers 20 and 2| constitute a capacita
tive potentiometer on the output circuit by which
35 a desired part of the voltage is supplied to the
detector valve. The condenser 20 serves simul
taneously as a grid condenser. for this detector
valve.
'
If a ?nal valve of very great power is used,‘
40. preferably an arrangement as shown in Fig. 2
may be utilized. In this arrangement use is
made of valves supplied with alternating cur
rent. The grid bias for the amplifying valve
is delivered by two recti?ers preferably housed
in one valve and having one common cathode.
The recti?er formed by the cathode 23 and the
anode 24 is connected to a winding 39 of the
public supply transformer 3| and consequently
delivers a constant recti?ed voltage.
The recti
50 ?er formed by the cathode 23 and the anode 25 is
connected to a part of the output impedance 9
of valve‘I so that this recti?er produces volt
ages the'value of which depends on the signal
voltage. The two recti?ed voltages are smoothed
in known manner, and are supplied in opposite
directions to the input circuit of the amplifying
,1.,In combination ‘with an audio frequency
ampli?er, an audio frequency signal input cir
cuit coupled to the ampli?er input electrodes, an
output circuit coupled to the output electrodes 20
of the ampli?er, a source of alternating current
potential, a diode recti?er coupled to said. source,
'a direct current connection between said input
circuit and the diode anode whereby the ampli
?er signal grid is maintained at a negative di 25
rect current potential with respect to the cath
ode, and means, responsive to variations in the
ampli?er output amplitude, for varying said sig
nal grid bias.
2. In combination with an audio frequency 30
ampli?er, an audio frequency signal input cir
cuit coupled to the ampli?er input electrodes, an
output circuit coupled to the output electrodes
of the ampli?er, a source of alternating current
potential, a diode recti?er coupled to said source, 35
and a direct current connection between said
input circuit and the diode anode whereby the
ampli?er signal grid is maintained at a negative
direct current potential with respect to the oath
ode, a second anode in the envelope of said di 40
ode, and a path of ‘low impedance to the audio
output of said ampli?er connected between the
ampli?er output circuit and said second anode.
3. In combination with an audio frequency
ampli?er, an audio frequency signal input cir
cuit coupled to the ampli?er input electrodes,
an output circuit coupled to the output elec
trodes of the ampli?er, a source of alternating
current potential, a diode recti?er coupled to
said source, and a direct current connection be
50
tween ‘said' input circuit and the diode anode
whereby the ampli?er signal grid is maintained
at a negative direct current‘ potential with re
spect ‘to the cathode, said diode being provided
with a second anode adjacent the diode cath 55
ode, a signal connection between the ampli?er
valve so that the bias of this valve varies in
output circuit and the second anode, said diode ,
the desired manner with the signalintensity.
The current from supply source 3| is recti?ed,
cathode and second anode being connected to
gether to‘providea diode recti?er for develop
60 and develops across resistor 40 a direct current
ing a biasing direct current voltage from am
voltage. Since the signal grid is connected to
the anode side of resistor 40, the signal grid is
pli?ed signal currents which biases said ampli
?er in a direction to increase the ampli?er plate
negatively biased to a constant value; as ex
current flow.
4. In, combination with a source of audio fre
quency signals, an audio frequency signal am
plained previously this‘ value is not great enough
65 to operate the tube I on the curved portion of
the characteristic- A portion of the signal en
ergy is recti?ed by diode 25—23; resistor 1H hav
ing developed thereacross a direct current volt
age proportional in magnitude to'the signal in
tensity. Since the resistor 4| is connected in
series between the cathode of tube I and re
sistor 40, and the positive end of the latter is
connected to- the positive terminal of resistor 4|,
the voltages across bothresistors oppose each
751 other. ,I-Ience, with increasing signal intensity
pli?er, a potential source for applying a c0n~
stant negative bias to the ‘amplifier grid suffi
cient in magnitude to adjust theampli?er oper
ation to a predetermined point on the linear
portion of the ampli?er grid potential-plate
current characteristic, a recti?er tube coupled to
the ampli?er output circuit to rectify audio sig—
nails, a resistor connected in the space current
path of said recti?er for'developing an ampli?er
grid biasing voltagewhich varies in magnitude
60
65
3
2,120,995
with the amplitude of the audio signals im
pressed on the recti?er, means for impressing
ampli?er tube and having a magnitude such that
said varying bias voltage on the ampli?er grid
the direct current voltage developed thereacross,
by recti?cation of said alternating current, is
in a sense to decrease said negative bias, and
su?icient to maintain said control grid at a pre
the magnitude of said Varying biasing voltage
being maintained Within such limits as to operate
the ampli?er over the linear portion solely of its
said characteristic.
determined negative direct current potential
with respect to the cathode, a second recti?er
5. In combination with an electric wave am
pli?er tube, a source of waves, to be ampli?ed.
coupled between the wave input grid and cath
ode of said tube, said cathode being at a rela
tively ?xed potential, a source of alternating
current energy, a recti?er circuit, including an
15 impedance, coupled to said alternating current
source, said impedance being connected in se
ries between the said grid and cathode of said
circuit, including an impedance, arranged to
have waves ampli?ed by said ampli?er im
pressed thereupon from the ampli?er output cir
cuit, said impedance being connected between 1O
the control grid and cathode of said ampli?er
tube and having a magnitude such that the di
rect current voltage developed thereacross, by
recti?cation of said ampli?ed waves, biases said
control grid in a positive direction with respect 15
to said cathode.
,
,
ABRAHAM VAN DE RIET.
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